This option enables you to specify what options to export/expose to JS. Some options are required to be exposed for the default logic to work but if you have written a custom theme/interface it could be useful to restrict or allow more of config options.

Example of usage in the config.php file

$mcImageManagerConfig['preview.allow_export'] = "urlprefix,urlsuffix";

Example of usage in the Web.Config file

<add key="preview.allow_export" value="urlprefix,urlsuffix" />